This invention relates to a brake system for a vehicle, and more particularly to a hydraulic brake system for applying selectively the same and different braking pressures to the front and rear brakes of the vehicle.
In a variety of vehicles, and especially in large earthmoving vehicles, or heavy material-carrying vehicles, such as, for example, tractor scrapers, there is always the need to provide adequate cooling to the brakes. Such cooling insures the continued operation of the brakes especially when said brakes are used to stop a fully loaded vehicle. Generally, a tractor scraper includes a front set of brakes associated with the front wheels of the tractor and a rear set of brakes associated with the rear wheels of the scraper. Cooling apparatus, operably associated with the engine means of the tractor, can be used to cool the front set of brakes. However, there is generally no cooling apparatus other than that designed into the tire and hub themselves, associated with the rear brakes of the scraper. This is due to the uneconomical expense of operably associating a cooling apparatus located in the scraper with the engine means located in the tractor. Further, any arrangement which did associate an engine means located in the tractor with the scraper cooling apparatus would require for example, universal pipe connectors or exposed flexible conduits, both of which are susceptable to breakage. A need for solving the cooling problem for a heavy material-carrying vehicle that is required to travel down long, steep grades, can easily be appreciated.